Polymeric compositions and intraocular lenses made from same

ABSTRACT

New high refractive index polymeric compositions and foldable intraocular lenses made from such compositions are disclosed. In one embodiment, the present compositions comprise a copolymer including a major amount of a first constituent derived from a first monomeric component the homopolymers of which have a refractive index of at least about 1.50, a minor amount of a second constituent derived from a second monomeric component other than the first monomeric component the homopolymers of which have a glass transition temperature of less than about 30° C., preferably less than about 22° C., and a third constituent derived from a crosslinking monomeric component in an amount effective to facilitate returning a deformed intraocular lens made of the composition to its original shape.

This application is a division of application Ser. No. 973,470 pending,filed Nov. 9, 1992.

BACKGROUND OF THE INVENTION

The present invention relates to polymeric compositions and tointraocular lenses made from such compositions. More particularly, theinvention relates to polymeric compositions which have high refractiveindexes and to intraocular lenses, preferably deformable intraocularlenses, made therefrom.

Intraocular lenses (IOLs) have been known for a long time, since shortlyafter the end of World War II. Such a lens is surgically implanted intoa mammalian eye, e.g., human eye, to replace a damaged or diseasednatural lens of the eye and restore the patient's vision.

Although IOLs are made from "hard" or "rigid" polymeric or glass opticalmaterials, such as polymethylmethacrylate (which has a refractive indexof 1.48), soft resilient polymeric materials, such as silicones, havebeen increasingly used, for the reasons discussed below, in ophthalmicapplications.

Since soft IOLs are deformable, for example, foldable or rollable, forimplantation, a smaller incision can be surgically cut in the eye thanfor the implantation of "hard" IOLs of the same optical power. Thesmaller the incision, the less trauma the patient's eye experiences andthe faster post-operative healing occurs. An incision of about 3 mm isideal since this size incision is presently required to remove thenatural lens after it has been broken up, for example, emulsified in aconventional phacoemulsification procedure. In contrast the typical IOLoptic has a diameter of about 6 mm.

The size and mechanical characteristics of the deformable IOLs play animportant role. As is well understood by those skilled in the art, forsuccessful implantation, the deformable IOL must have sufficientstructural integrity, elasticity and elongation and be small enough insize to permit deforming for insertion through a small incision. Afterinsertion, the lens must, of course, regain its original shape and havesufficient structural integrity to retain such shape under normal useconditions.

In general, the thinner the deformable IOL the smaller the incision inthe eye that is required. On the other hand, in order to functionoptically as an IOL, the lens must have sufficient optical refractorypower. Also, the higher the optical refractive index of the materialmaking up the IOL, the thinner the IOL can be and still obtain the sameoptical refractory power.

IOLs made of silicone polymeric materials conventionally have refractiveindexes which are no greater than about 1.46. Consequently, their centerthicknesses are substantially greater than those of IOLs composed ofmaterials having higher refractive indexes. Deformable IOLs made ofacrylic materials can be too rigid for use at room temperature, whichrigidity can result in cracking if the IOL is folded quickly; can benear silicone polymeric materials in refractive index; or can be quitetacky in nature, which tackiness inhibits deforming to a sufficientlysmall size for insertion through a very small incision and may causehandling problems.

Gupta U.S. Pat. No. 4,834,750 discloses IOLs with optics made ofcopolymers of methacrylate esters which form homopolymers that arerelatively hard at room temperature and acrylate esters which formhomopolymers that are relatively soft at room temperature. Suchcopolymers are crosslinked with a diacrylate ester to produce an acrylicmaterial having a tack-free surface and a glass transition temperaturein the range of -30° to 25° C. This patent discloses that such opticscan be deformed for insertion into the eye. However, this patent issilent on the refractive index of IOL optics and is, thus, unconcernedwith forming deformable IOLs with high refractive indexes. For example,none of the specific monomers disclosed in this patent providehomopolymers which have a refractive index of at least about 1.50.

It would be advantageous to provide an IOL material of constructionwhich has good optical properties, including optical clarity and highrefractive index, and has sufficient characteristics and properties toprovide an IOL which is effectively deformable for insertion through asmall incision.

SUMMARY OF THE INVENTION

New polymeric materials and IOLs produced from such polymeric materialshave been discovered by the present inventors. The present polymericmaterials are derived from a combination of monomers and provide veryuseful optical properties in terms of optical clarity and highrefractive index, and can be formed into IOLs which are effectivelydeformable, preferably foldable, for insertion through small surgicalincisions, preferably on the order of about 3 mm or less (in maximumtransverse dimension). Moreover, the present IOLs regain their originalshape in a reasonable period of time at conditions present in the eye.The present polymeric materials can be produced using conventionalmonomeric components and conventional techniques, e.g., conventionalpolymerization techniques. Thus, the present invention is very effectiveand easy to practice and results in polymeric materials and IOLs whichhave outstanding properties.

In one broad aspect, the present invention relates to compositions whichcomprise a copolymer including a first constituent, a second constituentand a third constituent. The first constituent is derived from amonomeric component the homopolymers of which have a refractive index ofat least about 1.50, which is a higher refractive index than methylmethacrylate homopolymer. The homopolymers of such first monomericcomponent are preferably rigid. The second constituent is derived from amonomeric component, other than the monomeric component from which thefirst constituent is derived, the homopolymers of which have a glasstransition temperature of less than about 30° C., preferably less thanabout 22° C. The third constituent is derived from a cross-linkingmonomeric component and is present in an amount effective to facilitatereturning a deformed IOL (deformed for implantation) made from thecomposition to its original shape, for example, at the conditionspresent in the human eye.

In another broad aspect of the present invention, IOLs are providedwhich are sized and adapted to be inserted, preferably in a deformedstate, through an incision, preferably an incision of about 3 mm, into amammalian eye for use. The IOLs of the present invention comprise thecompositions, as described herein.

These and other aspects of the present invention are set forth in thefollowing detailed description examples and claims, particularly whenconsidered in conjunction with the accompanying drawings in which likeparts bear like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an IOL in accordance with the presentinvention.

FIG. 2 is a side view of the IOL of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present compositions comprise copolymers including at least threeconstituents. The first constituent, which is preferably present in thepresent copolymers in an amount of at least about 10% or about 20% byweight and more preferably in a major amount (at least about 50%) byweight, is derived from a first monomeric component the homopolymers ofwhich have a refractive index of at least about 1.50, preferably atleast about 1.52 or about 1.54. The homopolymers of the first monomericcomponent preferably have a substantial degree of rigidity. The secondconstituent, which is preferably present in the present copolymers in anamount of at least about 3% or about 10% or about 20% by weight, isderived from a second monomeric component other than the first monomericcomponent. Homopolymers of the second monomeric component have a glasstransition temperature of less than about 30° C., preferably less thanabout 22° C.

The first and second constituents together are preferably at least about80%, more preferably at least about 90%, by weight of the presentcopolymers. The first and second monomeric components are preferablyselected so that each of these monomeric components can chemically reactwith the other monomeric component.

The third constituent of the present copolymers is derived from across-linking monomeric component, that is a monomeric component whichcan form cross-links in the present copolymers. This cross=linkingmonomeric component is preferably multi-functional and can chemicallyreact with both the first and second monomeric components. The thirdconstituent of the present copolymers is present in an amount effectiveto facilitate returning a deformed IOL made from the present compositionto its original shape, for example, in a reasonable period of time, atthe conditions present in the human eye.

The present copolymers are optically clear and have high refractiveindexes, for example, at least about 1.50, and preferably at least about1.52 or at least about 1.54. The combination of properties of thepresent copolymers, which allows the manufacture of effectivelydeformable IOLs having high optical power, is very advantageous.

As used herein, the term "homopolymer" refers to a polymer which isderived substantially completely from the monomeric component inquestion. Thus, such homopolymer includes as the primary, preferablysole, monomeric component, the monomeric component in question. Minoramounts of catalysts, initiators and the like may be included, as isconventionally the case, in order to facilitate the formation of thehomopolymer. In addition, the homopolymers of both the first monomericcomponent and the second monomeric component have sufficiently highmolecular weights or degrees of polymerization so as to be useful as IOLmaterials of construction.

The homopolymers of the first monomeric component are preferably rigid.An IOL made from such a "rigid" homopolymer is not deformable, forexample, using systems which are specifically structured and used todeform IOLs for insertion through a small incision into the eye. Therigidity of the homopolymer of the first monomeric constituent mayresult in an IOL made from such homopolymer being not deformable, orbreaking or otherwise deteriorating as a result of the application offorce seeking to so deform such IOL for implantation through a smallocular incision.

The first constituent is preferably present in an amount of at leastabout 10% or at least about 20%, more preferably in a major amount, byweight of the present copolymers. The first monomeric component fromwhich the first constituent is derived may be selected from compoundswhich meet the criteria set forth herein for such component. Thismonomeric component should be such as to provide the present copolymerswith increased refractive index relative to the homopolymers of thesecond monomeric component. The homopolymers of the first monomericcomponent have a refractive index of at least about 1.50, preferably atleast about 1.52 or at least about 1.54.

Of course, the first, second and third monomeric components should besuch as to provide copolymers which are compatible for use in the eye,are optically clear and are otherwise suitable for use as materials ofconstruction for IOLs. In one useful embodiment, each of the first,second and third monomeric components is substantially free of silicon,so that the resulting copolymer is not a silicone polymer. Eachmonomeric component useful in producing the present copolymerspreferably includes at least one a functional group containingcarbon-carbon unsaturation, more preferably a carbon-carbon double bond.The monomeric components may be substituted with substantially non-interfering substituents which have no substantial detrimental effect onthe copolymer produced therefrom. Such substituents may include one ormore elements, such as oxygen, nitrogen, carbon, hydrogen, halogen,sulfur phosphorus, and the like and mixtures and combinations thereof.

Particularly useful first monomeric components include styrene, vinylcarbazole, vinyl naphthalene, benzyl acrylate, phenyl acrylate, naphthylacrylate, pentabromophenyl acrylate, 2-phenoxyethyl acrylate,2-phenoxyethyl methacrylate, 2,3-dibromopropyl acrylate and mixturesthereof.

The second constituent is preferably present in an amount of at leastabout 2%, more preferably at least about 4% by weight of the copolymer.Any suitable second monomeric component which meets the criteria forsuch component set forth herein may be employed. Homopolymers of thesecond monomeric component have glass transition temperatures of lessthan about 30° C., preferably less than about 22° C. Particularly usefulsecond monomeric components include n-butyl acrylate, n-hexyl acrylate,2-ethylhexyl acrylate, 2-ethoxyethyl acrylate, 2,3-dibromopropylacrylate, n-1, 1-dihydroperfluorobutyl acrylate and mixtures thereof.

The third or crosslinking monomeric component is often present in aminor amount relative to the amounts of the first and second monomericcomponents. Preferably, the third constituent is present in thecopolymer in an amount of less than about 1% by weight of the copolymer.The third constituent of the present copolymers may be considered to bea crosslinker. The crosslinking monomeric component is often selectedfrom multifunctional components, preferably able to chemically reactwith at least one functional group of each of the first monomericcomponent and the second monomeric component. The crosslinking monomericcomponent is chosen to be chemically reactible with at least onefunctional group associated with one or both of the first monomericcomponent and the second monomeric component. Examples of usefulcrosslinking monomeric components include ethylene glycoldimethacrylate, propylene glycol dimethacrylate, ethylene glycoldiacrylate and the like and mixtures thereof.

In a particularly useful embodiment, the copolymers further include afourth constituent derived from a hydrophilic monomeric component, otherthan the first, second and third monomeric components. This fourthconstituent is present in an amount, preferably at least about 2% orabout 4% by weight of the copolymer, effective to reduce the tackinessof the copolymer relative to a substantially identical copolymer withoutthe fourth constituent. In addition, the presence of such a fourthconstituent may provide one or more other benefits, e.g., enhancedtensile strength and enhanced compatibility with the environment in theeye, relative to a substantially identical copolymer without the fourthconstituent. The fourth constituent is preferably present in an amountof less than about 15% by weight of the copolymer. Copolymers whichinclude about 15% by weight or more of a constituent derived fromhydrophilic monomeric components tend to form hydrogels when exposed towater., The present copolymers are preferably not hydrogel-forming. Theadvantageous properties of the present copolymers are preferably theresult of selecting the proper constituents in accordance with thepresent invention rather than forming a hydrogel from such copolymers.

As used herein, the term "hydrophilic monomeric component" refers tocompounds which produce hydrogel-forming homopolymers, that ishomopolymers which become associated with substantial amounts forexample at least about 20% based on the weight of the homopolymer, ofwater and which physically swell as a result of such Association.Specific examples of useful hydrophilic monomeric components includeN-vinyl pyrrolidone; hydroxyalkyl acrylates and hydroxyalkylmethacrylates, such as 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate,4-hydroxybutyl acrylate, 4-hydroxybutyl metharcylate,2,3-dihydroxypropyl acrylate, 2,3 -dihydroxypropyl methacrylate and thelike; acrylamide; N-alkyl acrylamides such as N-methyl acrylamide,N-ethyl acrylamide, N-propyl acrylamide, N-butyl acrylamide and thelike; acrylic acid; methacrylic acid; and the like and mixtures thereof.

In one embodiment, the first monomeric component is characterized asincluding one or more aryl-containing groups. Without wishing to limitthe present invention to any particular theory of operation, it isbelieved that the presence of such aryl-containing groups in the firstmonomeric component at least facilitates, and preferably leads to orresults in, the present copolymers having desirably high refractiveindexes. If the first monomeric component includes one or morearyl-containing groups, it is preferred that at least the secondmonomeric component, and more preferably that the second, third andfourth monomeric components, include no aryl-containing groups. It hasbeen found that the specific first monomeric component selected, and theamount of such component used to form the copolymer, can effectivelycontrol the refractive index of the copolymer. In other words, thepresent copolymers are provided with desirably high refractive indexeswithout requiring that the second monomeric component, or the second,third and fourth monomeric components, have high refractive indexescomparable to the refractive index of the first monomeric component.This "single refractive index control" is very effective in achievinghigh refractive index copolymers, and allows flexibility in selectingthe other monomeric component or components so that copolymers withadvantageous properties, other than refractive index, for example,copolymers formable into IOLs which can be effectively deformed (forinsertion) at room temperature, can be obtained.

The present copolymers may be produced using conventional polymerizationtechniques. For example, the monomers can be blended together and heatedto an elevated temperature to facilitate the polymerization reaction.Catalysts and/or initiators, for example, selected from materials wellknown for such use in the polymerization art, may be included in themonomer mix in order to promote, and/or increase the rate of, thepolymerization reaction. Examples of such initiators include 2,2'-azobis(2,4-dimethylpentanenitrile), 2,2'-azobis (2-methylpropanenitrile),2,2'-azobis (2-methylbutanenitrile), peroxides such as benzoyl peroxide,UV initiators such as diethoxyacetophenone, and the like and mixturesthereof. In addition, effective amounts of ultraviolet light absorbingmonomeric components, such as functional benzotriazole and benzophenonederivatives, may be included in the precursor monomer mix. Such UV lightabsorbing monomeric components are polymerized-into the final copolymerto provide the final copolymer with effective UV light absorbingproperties.

In one particularly useful embodiment, the present copolymers areproduced by mixing together the first monomeric component and the secondmonomeric component (and the fourth monomeric component, if any). Thismixture is well blended, deareated and heated to a temperature, forexample, of about 50° C. to about 80° C. and maintained at thistemperature for a period of time, for example, of about 15 minutes toabout 3 hours. The mixture undergoes partial polymerization to form aviscous liquid when cooled to about 25° C.

The final copolymer can be produced by combining this partiallypolymerized viscous liquid, the crosslinking monomeric component andcatalyst and/or an initiator. Alternately, all the monomeric componentsand catalyst and/or initiator can be combined or mixed together. Theviscous liquid, or monomeric mixture, is well blended, deareated andpoured into a mold. The mold is heated, preferably to a temperature ofabout 40° C. to about 100° C., and the liquid or mixture is allowed tocure, preferably for about 1 hour to about 24 hours. The material in themold is then post-cured, preferably at a temperature in the range ofabout 70° C. to about 130° C., for a period of time, preferably forabout 2 to about 30 hours. After curing (and post-curing), the mold isdisassembled and the molded optic recovered.

Alternately, the curing and post-curing occurs in a tube. The copolymerformed in the tube is cut into cylindrical lens blanks. The lens blankscan be machined to produce the finished optic. Such machining mayinvolve milling and lathing at cryogenic temperatures.

Referring now to FIGS. 1 and 2, IOL 21 is illustrated as including apair of radially outwardly extending haptics or fixation members 28secured to optically clear optic 26. Each haptic 28 has a substantiallyuniform cross section throughout its length and is shown provided with asmoothly curved region 32, intermediate a lens bonding region 34 and afree end region 36. Although the illustrated embodiment is provided withtwo opposing haptics 28, it is understood that an IOL having only onehaptic or more than two haptics bonded to the optic is within the scopeof the invention.

Optic 26 is made of a copolymer in accordance with the presentinvention, for example, the copolymer as set forth in Example 1 hereof.Optic 26 can be formed in accordance with conventional IOL optic formingtechniques, such as by injection molding and the like techniques.Alternately, the monomeric components can be first mixed in a tube andthen cured in the tube. The resulting rod then is cut into buttons whichare than cryolathed into IOL optics.

Typically, each haptic 28 comprises a flexible member comprising metalor, preferably, polymeric material, and having a substantially circularcross-section, although alternative cross-sectional configurations maybe substituted, if desired. Although the haptics may take on anysuitable configuration, the illustrated haptics 28 are relatively thinand flexible, while at the same time being sufficiently strong toprovide support for IOL 21 in eye 10. The haptics 28 may comprise any ofa variety of materials which exhibit sufficient supporting strength andresilience, and which are substantially biologically inert in theintended in vivo environment. Suitable materials for this purposeinclude, for example, polymeric materials such as polypropylene,polymethyl methacrylate, polycarbonates, polyamides, polyimides,polyacrylates, 2-hydroxymethylmethacrylate, poly (vinylidene fluoride)polytetrafluoroethylene and the like; and metals such as stainlesssteel, platinum, titanium, tantalum, shapememory alloys, e.g., nitonal,and the like. The haptics can be produced using conventional and wellknown forming techniques. For example, the preferred polymeric hapticscan be formed in accordance with known thermoplastic polymer formingtechniques, such as by injection molding or by extrusion.

The lens bonding regions 34 of the haptics 28, which, as describedherein, are secured to Optic, may be provided with any of a variety ofconfigurations, such as an anchoring loop, and anchoring "T", or otheranchor structure, to provide a mechanical interlock with the optic, suchas has been done in the prior art.

IOL 26 can be formed using any one of various techniques, such as thoseconventionally used to form IOLs. For example, the lens bonding regions34 of haptics 28 can be placed in a mold which is filled with a mix ofthe monomeric components used to form the optic 26. The mold is thensubjected to conditions, e.g., elevated temperature, effective to formthe copolymer of the present invention from this monomer mix. The lensbonding regions 34 become bonded to the optic 26, thereby securing thehaptics 28 to the optic. Alternately, the haptics 28 can be secured inrecesses provided in the already formed optic 26.

Optic 26 has a refractive index of at least about 1.50, and is foldablefor insertion into a human eye through an incision of about 3 mm inlength. After insertion into the eye in the folded condition, IOL 21returns to its original shape in a reasonable period of time, forexample, on the order of about 3 seconds or about 20 seconds to aboutthree minutes, and can be easily positioned in the eye for effective andlong term use as a replacement for the natural lens normally present inthe eye.

The following non-limiting examples illustrate certain aspects of thepresent invention.

EXAMPLE 1

The following formulation was blended, purged with nitrogen for 3minutes and then cured into a crosslinked copolymer.

    ______________________________________                                                             Weight %                                                 ______________________________________                                        2-phenoxyethyl acrylate                                                                              89.6                                                   n-hexyl acrylate       10.0                                                   ethylene glycol dimethacrylate                                                                       0.35                                                   2,2'-azobis (2,4-dimethylpentanenitrile)                                                             0.05                                                   2,2'-azobis(2-methylbutanenitrile)                                                                   0.05                                                   ______________________________________                                    

The cure temperature cycle used was as follows:

heat from 25° C. to 50° C. in 30minutes;

maintain at 50° C. for 5 hours;

heat from 50° C. to 90° C. in 4 hours;

maintain at 90° C. for 1 hour; and

cool from 90° C. to 25° C. in 6 hours.

The post-cure temperature cycle used was as follows:

heat from 25° C. to 120° C. in 3 hours;

maintain at 120° C. for 2 hours; and

cool from 120° C. to 25° C. in 3 hours.

The homopolymers of the 2-phenoxyethyl acrylate component have anoptical refractive index of about 1.56, and are relatively rigid. Forexample, while a one cm diameter rod of such a homopolymer was somewhatrubbery, when this rod was bent into a U-shape, it cracked at the baseof the U. Homopolymers of n-hexyl acrylate have a glass transitiontemperature of -58° C.

The resulting copolymer had a refractive index of 1.5365. A one cmdiameter rod of this copolymer was folded 180° with no cracking andreturned to its original shape within a few seconds.

EXAMPLE 2

Using conventional techniques, an IOL is formed including an optic madefrom the copolymer produced in Example 1 and haptics made ofpolypropylene filaments. In order to produce a 20 diopter, plano-convexoptic, having a 0.305 mm edge thickness and a 6.0 mm diameter, the opticcenter thickness is approximately 0.76 mm. This represents a substantialimprovement relative to the same type of lens made from a materialhaving a refractive index of 1.46, such as certain silicone materials.Using a silicone material having a refractive index of 1.46, the centerthickness of the optic is about 1.08 mm. This silicone optic, because ofits relatively high center thickness, is more difficult to fold relativeto the optic made of the copolymer produced in Example 1.

EXAMPLE 3

An IOL is produced having an optic as indicated in Example 2. Twosubstantially opposing haptics, such as shown in FIGS. 1 and 2, madefrom polypropylene filaments are bonded to this optic. The resulting IOLis inserted into the eye through a 3 mm surgical incision. In order toaccomplish such insertion, the IOL is folded. Upon being released intothe eye, the IOL regains its original shape in less than one minute andis fixed in position in the eye. After normal healing, the IOL iseffective and useful in the eye as a replacement for the natural lensnormally present in the eye.

EXAMPLE 4

The following formulation was blended, purged with nitrogen for 3minutes and then cured into a crosslinked polymer.

    ______________________________________                                                             Weight %                                                 ______________________________________                                        2-phenoxyethyl acrylate                                                                              89.3                                                   n-hexyl acrylate       5                                                      n-vinyl pyrrolidone    5                                                      ethylene glycol dimethacrylate                                                                       0.35                                                   2,2'-azobis (2,4-dimethylpentanenitrile)                                                             0.05                                                   2,2'-azobis (2-methylbutanenitrile)                                                                  0.05                                                   UV light absorbing component.sup.(1)                                                                 0.25                                                   ______________________________________                                         .sup.(1)                                                                      2-(2'-hydroxy-3'-t-butyl-5'-vinylphenyl)-5-chloro-2H-benzotriazole.      

The cure and post-cure temperature cycles used were as described inExample 1.

The resulting copolymer had a refractive index of about 1.55, and wasless tacky than the copolymer produced in Example 1. This copolymer hada tensile strength of 762±74 psi; an elongation at break of 143±61percent; and a modulus of 422±70 psi. A one cm diameter rod of thiscopolymer was folded 180° with no cracking and returned to its originalshape within a few seconds.

EXAMPLE 5

Using conventional techniques, an IOL is formed including an optic madefrom the copolymer produced in Example 4 and haptics made ofpolypropylene filaments. This IOL has a configuration substantially asshown in FIGS. 1 and 2.

The resulting IOL is inserted into the eye through a 3 mm surgicalincision. In order to accomplish such insertion, the IOL is folded. Uponbeing released into the eye, the IOL regains its original shape in lessthan 1 minute and is fixed in position in the eye. After normal healing,the IOL is effective and useful in the eye as a replacement for thenatural lens normally present in the eye.

while this invention has been described with respect to various specificexamples and embodiments, it is to be understood that the invention isnot limited thereto and that it can be variously practiced within thescope of the following claims.

What is claimed is:
 1. A composition comprising a copolymer including afirst constituent derived from a first monomeric component thehomopolymers of which have a refractive index of at least about 1.50,said first monomeric component including one or more aryl-containinggroups, a second constituent derived from a second monomeric componentother than said first monomeric component the homopolymers of which havea glass transition temperature of less than about 30° C., and a thirdconstituent derived from a crosslinking monomeric component in an amounteffective to facilitate returning a deformed intraocular lens made ofsaid composition to its original shape.
 2. The composition of claim 1wherein the homopolymers of said fist monomeric component have asubstantial degree of rigidity and the homopolymers of said secondmonomeric component have a glass transition temperature of less thanabout 22° C.
 3. The composition of claim 1 wherein said copolymer isoptically clear and has a refractive index of at least about 1.50. 4.The composition of claim 1 wherein said first constituent is a majoramount of said copolymer, and said first constituent and said secondconstituent together are at least about 80% by weight of said copolymer.5. The composition of claim 1 wherein neither said second monomericcomponent nor said third monomeric component include any aryl-containinggroups.
 6. The composition of claim 1 wherein said copolymer furtherincludes a fourth constituent derived from a hydrophilic monomericcomponent other than said first, second and third monomeric components,said fourth constituent being present in an amount effective to reducethe tackiness of said copolymer relative to a substantially identicalcopolymer without said fourth constituent.
 7. The composition of claim 1wherein each of said first, second and third monomeric componentsincludes at least one functional group containing carbon-carbonunsaturation.
 8. The composition of claim 1 wherein each of said first,second and third monomeric components includes at least one functionalgroup containing a carbon-carbon double bond.
 9. The composition ofclaim 1 wherein said first monomeric component is selected from thegroup consisting of styrene, vinyl carbazole, vinyl naphthalene, benzylacrylate, phenyl acrylate, naphthyl acrylate, pentabromophenyl acrylate,2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, and mixturesthereof, and said second monomeric component is selected from the groupconsisting of n-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate,2-ethoxyethyl acrylate, 2,3-dibromopropyl acrylate, n-1,1-dihydroperfluorobutyl acrylate and mixtures thereof.
 10. Thecomposition of claim 1 wherein said first constituent is a major amountby weight of said copolymer.
 11. The composition of claim 6 wherein saidhydrophilic monomeric component is selected from the group consisting ofN-vinyl pyrrolidone, hydroxyalkyl acrylates, hydroxyalkyl methacrylates,acrylamide, N-alkyl acrylamides and mixtures thereof.
 12. Thecomposition of claim 6 wherein said copolymer is optically clear and hasa refractive index of at least about 1.50.
 13. The composition of claim6 wherein said first constituent is a major amount of weight of saidcopolymer.
 14. The composition of claim 6 wherein neither said secondmonomeric component nor said third monomeric component include anyaryl-containing groups.
 15. A composition comprising a copolymerincluding a first constituent derived from a first monomeric componentthe homopolymers of which have a refractive index of at least bout 1.50,said first monomeric component being selected from the group consistingof styrene, vinyl carbazole, vinyl naphthalene, benzyl acrylate, phenylacrylate, naphthyl acrylate, pentabromophenyl acrylate, 2-phenoxyethylacrylate, 2-phenoxyethyl methacrylate, 2,3-dibromopropyl acrylate andmixtures thereof, a second constituent derived from a second monomericcomponent other than said first monomeric component the homopolymers ofwhich have a glass transition temperature of less than about 22° C., anda third constituent derived from a crosslinking monomeric component inan amount effective to facilitate returning a deformed intraocular lensmade of said copolymer to its original shape.
 16. The composition ofclaim 15 wherein said second monomeric component is selected from thegroup consisting of n-butyl acrylate, n-hexyl acrylate, 2-ethylhexylacrylate, 2-ethoxyethyl acrylate, 2,3-dibromopropyl acrylate, andmixtures thereof.
 17. The composition of claim 15 wherein said copolymerfurther includes a fourth constituent derived from a hydrophilicmonomeric component other than said first, second and third monomericcomponents, said fourth constituent being present in a amount effectiveto reduce the tackiness of said copolymer relative to a substantiallyidentical copolymer without said further constituent.
 18. A compositioncomprising a copolymer including a first constituent derived from afirst monomeric component the homopolymers of which have a refractiveindex of at least about 1.50, a second constituent derived from a secondmonomeric component other than said fist monomeric component thehomopolymer of which have glass transition temperature of less thanabout 22° C., said second monomeric component is selected from the groupconsisting of n-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate,2-ethoxyethyl acrylate, 2,3-dibromopropyl acrylate and mixtures thereof,and a third constituent derived from a crosslinking monomeric componentin an amount effective to facilitate returning a deformed intraocularlens made of said copolymer to its original shape.
 19. The compositionof claim 18 wherein said copolymer further includes a fourth constituentderived from a hydrophilic monomeric component other than said first,second and third monomeric components, said fourth constituent beingpresent in an amount effective to reduce the tackiness of said copolymerrelative to a substantially identical copolymer without said furtherconstituent.